Jodi Gilchrist

Head-to-Head Comparison of Second-Generation Nucleic Acid Amplification Tests for Detection of Chlamydia trachomatis and Neisseria gonorrhoeae on Urine Samples from Female Subjects and Self-Collected Vaginal Swabs

ABSTRACT In a comparison of 4 second-generation nucleic acid amplification tests performed with self-collected vaginal swab (SCVS) and first-void urine (FVU) specimens from 575 women, SCVS specimens indicated more infections than did FVU specimens in all assays. The prevalence rates were 9% (53/575 patients) for Chlamydia trachomatis and 2% (11/575 patients) for Neisseria gonorrhoeae. The clinical sensitivities for testing SCVS specimens for C. trachomatis were 98.1% on a Tigris system and 96.2% on a Panther system for the Aptima Combo 2 assay (Hologic Gen-Probe), 98.0% for the RealTime CT/NG assay on an m2000 instrument (Abbott), 90.6% for the ProbeTec CT/GC Q x assay on the Viper system (Becton Dickinson), and 84.6% for the cobas CT/NG assay on the cobas 4800 platform (Roche). Clinical sensitivities for C. trachomatis in FVU specimens were 88.7% (Tigris) and 88.0% (Panther) for the Aptima Combo 2 assay, 76.9% for the RealTime CT/NG assay, 75.5% for the ProbeTec CT/GC Q x assay, and 81.1% for the cobas CT/NG assay. Clinical sensitivities of the assays for N. gonorrhoeae, with limited positive results, ranged from 63.6% to 100%. Specificities for both infections ranged from 98.4 to 100%. Differences in analytical sensitivities and levels of molecular targets in clinical samples but not inhibitors of amplification may explain the differences in clinical sensitivities.

Workflow and Maintenance Characteristics of Five Automated Laboratory Instruments for the Diagnosis of Sexually Transmitted Infections

ABSTRACT The choice of a suitable automated system for a diagnostic laboratory depends on various factors. Comparative workflow studies provide quantifiable and objective metrics to determine hands-on time during specimen handling and processing, reagent preparation, return visits and maintenance, and test turnaround time and throughput. Using objective time study techniques, workflow characteristics for processing 96 and 192 tests were determined on m2000 RealTime (Abbott Molecular), Viper XTR (Becton Dickinson), cobas 4800 (Roche Molecular Diagnostics), Tigris (Hologic Gen-Probe), and Panther (Hologic Gen-Probe) platforms using second-generation assays for Chlamydia trachomatis and Neisseria gonorrhoeae. A combination of operational and maintenance steps requiring manual labor showed that Panther had the shortest overall hands-on times and Viper XTR the longest. Both Panther and Tigris showed greater efficiency whether 96 or 192 tests were processed. Viper XTR and Panther had the shortest times to results and m2000 RealTime the longest. Sample preparation and loading time was the shortest for Panther and longest for cobas 4800. Mandatory return visits were required only for m2000 RealTime and cobas 4800 when 96 tests were processed, and both required substantially more hands-on time than the other systems due to increased numbers of return visits when 192 tests were processed. These results show that there are substantial differences in the amount of labor required to operate each system. Assay performance, instrumentation, testing capacity, workflow, maintenance, and reagent costs should be considered in choosing a system.

Self-collected swabs of the urinary meatus diagnose more Chlamydia trachomatis and Neisseria gonorrhoeae infections than first catch urine from men

Objectives To compare first catch urine (FCU) and self-collected urinary meatal swabs for the detection of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) using the APTIMA Combo 2 assay. Methods A total of 511 young men from a high risk street youth clinic were studied. Group A (n=293) collected a FCU and a meatal APTIMA swab followed by Group B (n=218) who collected a FCU and two meatal samples using an APTIMA swab and a flocked swab. Order of sample collection was alternated. Individuals in Group B rated collection as easy, difficult or neither, then expressed a preference for sampling and swab type. All subjects performed meatal self-collection in the presence of a study monitor. Results The combined CT prevalence was 7.8% and 2.7% for NG where 80% of the men were without symptoms. Meatal swabbing identified 35 cases of CT and 14 cases of NG compared to 33 and 11 for FCU. Flocked and APTIMA swabs were equally effective in detecting more cases. The majority of men found self-collection of meatal swabs and urine to be easy. Although 63% preferred urine sampling, 60% of those who preferred swabbing selected the flocked swab. Conclusions Collection of meatal swabs could serve as an alternative to urethral swabbing and FCU for the detection of CT and NG.

Aptima Combo 2 Testing Detected Additional Cases of Neisseria gonorrhoeae Infection in Men and Women in Community Settings

ABSTRACT Aptima Combo 2 (AC2) Neisseria gonorrhoeae testing of 81,405 patients who were tested by culture and 14,666 who were AC2 tested for Chlamydia trachomatis detected 142 extra infections and confirmed 106 culture-positive samples (the positivity rate increased from 0.13 in testing by culture to 0.26 in testing by AC2). Retrievable AC2 positive samples were confirmed (98.5%) by an alternate AGC test.

Evaluation of a new APTIMA specimen collection and transportation kit for high-risk human papillomavirus E6/E7 messenger RNA in cervical and vaginal samples.

Background An APTIMA specimen collection and transportation (SCT) kit was developed by Hologic/Gen-Probe. Objectives To compare cervical SCT samples to PreservCyt and SurePath samples and self-collected vaginal samples to physician-collected vaginal and cervical SCT samples. To determine ease and comfort of self-collection with the kit. Study Design Each woman (n = 580) self-collected a vaginal SCT, then filled out a questionnaire (n = 563) to determine ease and comfort of self-collection. Colposcopy physicians collected a vaginal SCT and cervical PreservCyt, SCT, and SurePath samples. Samples were tested by APTIMA HPV (AHPV) assay. Results Agreement between testing of cervical SCT and PreservCyt was 91.1% (&kgr; = 0.82), and that of SurePath samples was 86.7% (&kgr; = 0.72). Agreement of self-collected vaginal SCT to physician-collected SCT was 84.7% (&kgr; = 0.68), and that of self-collected vaginal to cervical SCT was 82.0% (&kgr; = 0.63). For 30 patients with CIN2+, AHPV testing of cervical SCT was 100% sensitive and 59.8% specific compared with PreservCyt (96.6% and 66.2%) and SurePath (93.3% and 70.9%). Vaginal SCT sensitivity was 86.7% for self-collection and 80.0% for physician collection. Most patients found that vaginal self-collection was easy, 5.3% reported some difficulty, and 87.6% expressed no discomfort. Conclusions Cervical samples collected with the new SCT kit compared well to traditional liquid-based samples tested by AHPV. Although there was good agreement between self-collected and physician-collected samples with the SCT, in a limited number of 30 women, vaginal sampling identified fewer with CIN2+ precancerous cervical lesions than cervical SCT sampling. Comfort, ease of use, and detection of high-risk HPV demonstrated that the kit could be used for cervical and vaginal sampling.

Comparison of dacron and nylon-flocked self-collected vaginal swabs and urine for the detection of Trichomonas vaginalis using analyte-specific reagents in a transcription-mediated amplification assay

Objectives To compare self-collected vaginal swab (SCVS) types and first-catch urine (FCU) to diagnose Trichomonas vaginalis using analyte-specific reagents designed to be used in a transcription-mediated amplification assay. Methods A total of 241 women (group A) collected a FCU and a SCVS using a dacron swab (APTIMA collection kit). A second group of 289 women (group B) collected two SCVS using one dacron swab and one nylon-flocked swab. Results Of 75 young women (street youth) determined to be infected with T vaginalis only seven reported symptoms of vaginal discharge or irritation. Using a cutoff of 50 000 relative light units, the sensitivity and specificity was 97.2% and 97.6%, respectively for dacron SCVS compared with 41.7% and 100% for FCU in group A; 92.3% and 98.8% for dacron SCVS and 92.3% and 99.2% for flocked-nylon SCVS in group B. The assay tested 96 samples in 6 h. Conclusions Dacron and nylon-flocked SCVS performed equally well and significantly better than FCU using analyte-specific reagents in the APTIMA transcription-mediated amplification assay. Either swab type could be used for self-collection.

Comparison of Three Assays for Detection of Chlamydia trachomatis and Neisseria gonorrhoeae in SurePath Pap Samples and the Role of Pre- and Postcytology Testing

ABSTRACT Chlamydia trachomatis and Neisseria gonorrhoeae are common causes of sexually transmitted infections, and there is interest in screening SurePath liquid-based Pap (L-Pap) samples with Aptima Combo 2 (AC2), Amplicor (AMP), and ProbeTec ET (PT) assays. SurePath L-Pap samples and a cervical swab (CS) were collected from 394 women attending health clinics in Hamilton and Toronto, ON, Canada. L-Pap samples were tested with the three assays prior to being processed for cytology, and the CS sample was tested with AC2. The prevalence of C. trachomatis was 8.9%, and that of N. gonorrhoeae was 1.5%. By using the positives from CS testing, as well as CS negatives corresponding to L-Pap samples that tested positive in 2 of 3 assays, the sensitivities of AC2, AMP, and PT for C. trachomatis in precytology samples were calculated to be 97.1% (34 of 35 positive samples were detected), 91.4% (32 of 35 were detected), and 77.1% (27 of 35 were detected), respectively. Six women were infected with N. gonorrhoeae. After cytology processing, the results of testing the remaining liquid in the L-Pap vial and the cell-enriched fraction for C. trachomatis by AC2 showed positive agreements of 98.9% (kappa [k], 0.93) and 98.7% (k, 0.92), respectively, with the results of testing precytology L-Pap samples. Although all testing showed high specificity, testing for C. trachomatis by AC2 was significantly more sensitive than testing by PT for SurePath samples (P = 0.02). Newer versions of AMP (Cobas 4800) and PT (Q x with XTR technology) need published evaluations for detecting C. trachomatis and N. gonorrhoeae in L-Pap samples. C. trachomatis testing can be performed with similar results on pre- and postcytology SurePath samples.

Comparison of Flocked and Aptima Swabs and Two Specimen Transport Media in the Aptima Combo 2 Assay

ABSTRACT Self-collected vaginal Aptima swabs and flocked swabs in Aptima specimen transport medium and ESwabs in ESwab medium detected all 37 Chlamydia trachomatis-infected patients from 287 women tested by the Aptima Combo assay. Prevalence rates of C. trachomatis, Neisseria gonorrhoeae, and dual infection were 12.8%, 3.1%, and 2.4%, respectively.

Comparison of cobas 4800, m2000, Viper XTR, and Infinity 80 Automated Instruments When Processing Urine Specimens for the Diagnosis of Chlamydia trachomatis and Neisseria gonorrhoeae

Objectives North American and European advisory groups recommend testing for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) with nucleic acid amplification tests. Testing is often performed on automated instruments. The objectives of this study were to process urines for the diagnosis of CT and NG and to examine workflow procedures and outcomes. Methods While processing 1, 24, 48, 96, and 192 urine specimens on 3 batch-mode systems which use 96-well plates: cobas 4800, m2000, and Viper XTR and the random access cartridge testing GeneXpert Infinity 80, we measured assay performance, hands-on time for processing and maintenance, reagents and plastics consumption, time required to obtain results, and testing accuracy. Results The Infinity 80 required the least hands-on time for single specimens and smaller batches, whereas the Viper XTR and m2000 required the most hands-on time for all batch sizes. Cumulative daily, weekly, and monthly maintenance was highest for the Viper XTR and lowest for Infinity 80. All batch-mode instruments consumed large amounts of disposables. Time to results was shortest for the Infinity 80, and the Viper XTR provided the shortest time for the batch-mode instruments. All systems showed similar diagnostic accuracy. Conclusions Because detection performances were similar, issues of hands-on time, maintenance, time to results, and consumables are important operational factors for the diagnosis and treatment of CT/NG infections.

Detection of cervical precancerous lesions with Aptima HPV assays using SurePath preservative fluid specimens

SurePath specimens from women referred to colposcopy were treated with Aptima Transfer Solution (ATS) before testing in Aptima HPV (AHPV) and Aptima HPV 16, 18/45 (AHPV-GT) assays. Untreated SurePath specimens were tested with the cobas HPV test. PreservCyt specimens were assessed for cytology and tested with AHPV. High-grade cervical intraepithelial neoplasia lesions served as the reference standard. Excellent agreement (95.5%; k=0.91) was observed for ATS-treated SurePath specimens between Tigris and Panther systems and between the PreservCyt and ATS-treated SurePath specimens (91.1%, k=0.81) with the AHPV assay on Tigris. Agreement between the AHPV and cobas assays with SurePath specimens was substantial (89.9%, k=0.80). AHPV sensitivity for CIN2+(n=147) was 91.2% for SurePath and PreservCyt. Cobas HPV sensitivity was 93.9% for SurePath specimens. AHPV testing of SurePath specimens was more specific (59.4%) than cobas (54.7%) (p<0.001). Detection and genotyping showed similar absolute and relative risks. ATS-treated SurePath specimens tested with AHPV and AHPV-GT assays showed similar performance with greater specificity than cobas HPV on SurePath specimens. Similar overall results were seen using a CIN3 disease endpoint.